1. Field
The present disclosure relates generally to batteries, and more particularly, to lithium-ion polymer batteries.
2. Background
In an age when mobility is essential, large and heavy batteries are no longer acceptable. Technology has responded with the emergence and development of a new type of battery. Lithium-ion polymer batteries employ a relatively new technology to offer higher energy density, greater safety and lower weight than traditional lithium-ion rechargeable batteries.
Traditional lithium-ion batteries use a lithium salt electrolyte held in an organic solvent. The solvent is flammable, hazardous, difficult to handle, and must be encased in durable enclosures that increase battery weight. Lithium-ion polymer batteries, on the other hand, hold the lithium salt electrolyte in a dry solid polymer composite. This electrolyte resembles a plastic-like film that does not conduct electricity but allows the exchange of ions (electrically charged atoms or groups of atoms) between the battery's electrodes. One electrode is called the “cathode.” The cathode produces ions when negative polarity, applied to drive the battery, causes an electrochemical reaction and reduction of the cathode material. The other electrode is called the “anode.” The anode produces electrons through oxidation, which occurs when the anode material reacts with the electrons that were released from the cathode. The electrons pass from cathode to anode through the solid polymer composite. Unlike solvent-based electrolytes, the solid polymer composite used in lithium-ion polymer batteries is light, non-flammable and capable of being sealed in thin, flexible packaging instead of the traditional heavy casings. Therefore, lithium-ion polymer batteries can offer higher energy density, lower weight, and specialty shaping to enable slim geometry and fit virtually any application.
Unfortunately, lithium-ion polymer battery technology still has many hurdles to overcome before it can be effectively utilized on a large scale. These batteries are expensive to manufacture, and impractical to produce in commercially viable quantities, for a number of reasons that are unique to this new technology. Even those batteries able to be produced in small quantities do not achieve their full potential because limitations in current manufacturing techniques contribute to deterioration of battery performance and cycle life characteristics.
For example, battery quality may be compromised in the event a defective electrode is used in the battery cell stack. When electrodes coated with polymer electrolyte film are manufactured in large batches, some percentage of the electrodes produced may be defective for one or more reasons. For example, an imperfection in the polymer electrolyte film may leave the electrode insufficiently insulated so that it might cause an electrical short. However, there not currently and effective and efficient method for testing the viability of individual electrodes prior to their incorporation in a battery cell stack. These defective electrodes may therefore be unknowingly used when assembling battery stacks. Unfortunately, if battery quality is insufficient due to one electrode, or even a small number of electrodes, the entire battery must be discarded. This means that even good electrodes are discarded. Good electrodes cannot be easily separated from the faulty ones once the battery has been assembled. Therefore, discarding batteries that have electrical shorts due to faulty electrodes results in the waste of good electrodes and the reduction of manufacturing throughput.